Tiller dynamics and yield contribution in seed crops of Bromus inermis and Festuca pratensis established on different dates and with different plant densities

Abstract

Tiller demography and contribution to seed yield were studied in first year seed crops of Bromus inermis ‘Løfar’ and Festuca pratensis ‘Salten’ planted on different dates and with increasing plant densities (A: 15 or 18 Jun/11 plants m−2, B: 15 or 30 July/44 plants m−2, C: 15 August or 10 September/178 plants m−2) in field trials at Landvik, SE Norway, in 1998 and 1999. While the total tiller population in most crops increased until seed harvest, it decreased during panicle elongation in crops of Bromus inermis and Festuca pratensis that had reached 2000 and 3500 tillers m−2 in early spring, respectively. Except for the fact that many of the primary tillers of Bromus inermis died after producing barren stems, tillers formed in August and September had the greatest chance of becoming reproductive and produced the longest stems with the heaviest inflorescences in both species. Most tillers produced in winter or early spring either remained vegetative or died, but spring-emerging tillers contributed up to 30% of the total seed yield in early-established, low-density crops of Festuca pratensis. The results are discussed in relation to former papers suggesting that inter-tiller transfer of flower induction stimuli is possible in some perennial grasses. It is concluded that tillers produced in winter and spring contribute more to seed yield in Festuca pratensis than in Bromus inermis.